# NTSB DEN04IA026: Boeing 737-3M8, N303FL, Denver, CO, November 29, 2003 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: November 29, 2003, 08:40 local (15:40 UTC) - Place: Denver, CO - Coordinates: 39.858333, -104.666946 - Nearby events: https://openairdocs.org/map.md?lat=39.8583&lon=-104.6669&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 135 uninjured - Status: Completed, report June 2, 2004 - Report: Approved by Office Director - Parties: FAA Flight Standards District Office - NTSB case key (mKey): 58411 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN04IA026 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/58411/pdf - Page: https://openairdocs.org/ntsb/DEN04IA026 ## Probable cause The restricted movement of the flight control yoke and tiller wheel steering for reasons undetermined. ## Analysis While on final approach approximately 1/4 mile from the end of the runway, the captain applied right aileron to correct for a crosswind. He said the control yoke felt like it had "bound up." He used "excessive pressure" to get the control yoke to respond. An uneventful landing was made. During taxi, the captain cycled the control yoke left and right. After a few cycles, it seemed to move freely. He made an intentional sharp left turn and the tiller wheel seemed to "bind up." Mechanics performed a nose landing gear wheel steering test, and checked the cable tension to the nose wheel steering. A leak was discovered in the right hand nose steering accumulator, but the leak was "within limits." The case drain plugs and filters and the left and right hand aileron cables from the main wheel well outboard were inspected. Following flight control movement card 7-9002, mechanics performed an aileron PCU internal leak check. No discrepancies were noted. The airplane was then test flown and was returned to service. No data was recovered from the DFDR that would explain the event as described by the captain. ## Factual narrative On November 29, 2003, at 0840 mountain standard time, a Boeing 737-3M8, N303FL, operating as Frontier Airlines flight 567, experienced a momentary lock up of the captain and first officer's aileron and flight spoiler controls, while on final approach into Denver International Airport (DEN), Denver, Colorado. The airline transport certificated captain and first officer, 3 cabin crewmembers, and 130 passengers were not injured. Visual meteorological conditions prevailed. The scheduled domestic passenger flight was being conducted under the provisions of Title 14 CFR Part 121. An instrument flight rules (IFR) flight plan had been filed for the flight that departed Milwaukee, Wisconsin, at 0637 central standard time. The captain reported that they were on final approach approximately 1/4 mile from the end of the runway when he applied right aileron to correct for a crosswind. "The [control] yoke felt like it had 'bound up'." He had to use excessive pressure to get the control yoke to respond. An uneventful landing was made at DEN. After landing, he cycled the yoke left and right. After a few cycles, it seemed to free up. The captain said that while taxiing to parking with the number 2 engine shut down, he made a sharp left turn and the tiller [wheel] seemed to "bind up." After the passengers had deplaned, the airplane was taken to Frontier's maintenance hangar where mechanics performed a "[nose landing gear] wheel steering test [in accordance with Maintenance Manual] 32-51-00. Checked good. Performed cable tension to nose wheel steering [in accordance with Maintenance Manual] 32-51-00. Tension good. Found [right hand] nose steering accumulator leaking. Leak limits good [in accordance with Maintenance Manual] 29-00-00, page 605. Inspected case drain filters. Found no discrepancies [reference Maintenance Manual 24-15-91]. Removed and reinstalled #2 engine case drain plug to inspect. Found no discrepancies [reference Maintenance Manual 29-15-00]. Inspected [left hand] and [right hand] aileron cables from main [wheel well] outboard visually. No discrepancies noted. Complied with flight control movement card 7-9002. No discrepancies noted. Performed aileron PCU internal leak check procedure [reference Maintenance Manual 84-00-00. No discrepancies noted. Aircraft is released for operational check flight. Performed post operational check flight, walk around inspection." During the test flight, no discrepancies were noted and the airplane was returned to service. The digital flight data recorder (DFDR) was removed from the airplane and sent to NTSB's Vehicle Recorder Laboratory for readout. According to the DFDR engineer, no data was recovered that would explain the event as described by the captain. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, approach - flt control syst,yoke/control stick - movement restricted - landing gear,steering system - movement restricted - reason for occurrence undetermined (cause) ## Aircraft - Registration: N303FL (not matched to a registry record) - Reported make and model: Boeing 737-3M8 - Category: Airplane - Serial number: 25039 - Airframe hours: 38084 - Engines: General Electric CFM-563B2 20000 lbs thrust turbo fan; General Electric CFM-56-3B2 20000 lbs thrust turbo fan - Damage: No damage - Flight: Part 121 - Operator: Frontier Airlines Inc - Registered owner: Wells Fargo Bank Northwest NA Trustee - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, November 19, 2003, 88 hours before - Departed: MKE, Milwaukee, WI - Destination: DEN, Denver, CO - Flight plan: IFR - Airport: DEN, Denver International ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 50; injuries: none; airline transport, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; last flight review September 6, 2003; seat: left; flight hours: 144 in the last 90 days, 40 in the last 30 days - Co-pilot; age 45; injuries: none; commercial, airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; last flight review March 9, 2003; seat: right; flight hours: 5,600 total, 1,424 in this make and model, 3,321 as pilot in command, 176 in the last 90 days, 62 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 210° at 11 knots - Visibility: 10 statute miles - Lowest ceiling: 250,000 ft broken - Temperature: 55 °F, dew point 16 °F - Altimeter: 29.94 inHg - Observed at: DEN From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.